EP1882332B1 - Phasenregelung in einem mehrkanal-quantenkommunikationssystem - Google Patents

Phasenregelung in einem mehrkanal-quantenkommunikationssystem Download PDF

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Publication number
EP1882332B1
EP1882332B1 EP06769881A EP06769881A EP1882332B1 EP 1882332 B1 EP1882332 B1 EP 1882332B1 EP 06769881 A EP06769881 A EP 06769881A EP 06769881 A EP06769881 A EP 06769881A EP 1882332 B1 EP1882332 B1 EP 1882332B1
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Prior art keywords
signal
quantum
phase
receiver
frequency components
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French (fr)
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EP1882332A1 (de
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Mihaela Dinu
Christophe J. Dorrer
Randy Clinton Giles
Inuk Kang
Dan Mark Marom
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Alcatel Lucent SAS
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Alcatel Lucent SAS
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
    • H04L9/0852—Quantum cryptography
    • H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding

Definitions

  • the present invention relates to optical communication equipment and, more specifically, to equipment for transmission of encrypted data using quantum cryptography.
  • Cryptography is often used to exchange messages between two or more nodes (users, stations) in enhanced or even perfect privacy.
  • a typical cryptographic method employs a publicly announced encrypting/decrypting algorithm, with the confidentiality of transmitted information provided by a secret key used in conjunction with that algorithm.
  • a secret key is a randomly chosen, sufficiently long sequence of bits known only to the transmitting and receiving parties.
  • the transmitting station encrypts information using the secret key and sends the encrypted data over a public channel to the receiving station.
  • the receiving station uses the same key to undo the encryption and recover the original information.
  • DES Data Encryption Standard
  • a quantum channel can be established using, e.g., (i) a train of single photons propagating through an optical fiber, with key bits encoded by the photon's polarization or phase, or (ii) a train of coherent optical pulses, each containing a small number (e.g., less than a few hundred) of photons, with key bits encoded by quadrature values of selected variables characterizing each pulse. More details on the establishment and use of representative quantum channels can be found, e.g., in a review article by N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, entitled “Quantum Cryptography,” published in Reviews of Modem Physics, 2002, vol. 74, pp. 145-195 or in the US patent document US5675648 .
  • QKD quantum-key distribution
  • a current commercially available QKD system offers a QKD rate of about 1.5 kb/s over a single-mode optical fiber having a length of about 25 km.
  • a representative classical communication system offers a data transmission rate of about 10 Gb/s over an optical fiber having a length of about 1000 km. Given these parameters for the QKD and classical systems, one finds that significant improvements in QKD rate and/or transmission distance are desirable.
  • the receiver comprises an optical modulator (OM), a homodyne detector, and a signal processor.
  • the OM is adapted to phase-shift a local oscillator (LO) signal generated at the receiver.
  • the homodyne detector is adapted to (i) combine the LO signal with a quantum-information (QI) signal received via the transmission link from the transmitter to produce two interference signals and (ii) measure the intensity difference between these interference signals.
  • the processor is adapted to process the measurement result to generate a control signal, which causes the phase shift(s) produced in the OM to establish a phase lock between the LO and QI signals.
  • the QI signal has (i) a plurality of pilot frequency components, each carrying a training signal, and (ii) a plurality of QKD components, each carrying quantum key data; and the LO signal has corresponding pilot and QKD frequency components.
  • the receiver is adapted to phase-lock the pilot frequency components of the QI and LO signals by phase-shifting each pilot frequency component of the LO signal using a reference phase shift determined for that frequency component based on the corresponding training signal of the QI signal.
  • the receiver is further adapted to phase-lock the QKD frequency components of the QI and LO signals by phase-shifting each QKD frequency component of the LO signal using an approximated reference phase shift derived from the reference phase shifts for the pilot frequency components.
  • a system of the invention can maintain a phase lock for the QKD frequency components of the QI and LO signals, while the QKD frequency components of the QI signal continuously carry quantum key data.
  • the present invention is a receiver for a communication system adapted for transmission of quantum information and having a transmitter coupled to the receiver via a transmission link, wherein the receiver is adapted to: (i) receive via the transmission link a quantum-information (QI) signal generated by the transmitter using a first optical source; and (ii) phase-lock to the QI signal a local oscillator (LO) signal generated using a second optical source.
  • QI quantum-information
  • LO local oscillator
  • the present invention is a communication system for transmission of quantum information, comprising a transmitter coupled to a receiver via a transmission link, wherein the receiver is adapted to: (i) receive via the transmission link a quantum-information (QI) signal generated by the transmitter using a first optical source; and (ii) phase-lock to the QI signal a local oscillator (LO) signal generated using a second optical source.
  • QI quantum-information
  • LO local oscillator
  • Fig. 1 schematically shows a multi-channel quantum communication system 100 according to one embodiment of the invention. More specifically, system 100 is adapted to use wavelength (frequency) division multiplexing for quantum-key distribution (QKD).
  • System 100 has a transmitter 110 (Alice) and a receiver 130 (Bob) coupled via a transmission link (e.g., an optical fiber) 120.
  • Transmitter 110 has an optical-frequency comb source (OFCS) 112 coupled to an optical modulator (OM) 116.
  • OFCS 112 generates an optical signal 114 having a plurality of uniformly spaced frequency components.
  • OM 116 is a multi-channel optical modulator adapted to independently modulate each frequency component of signal 114 to produce a frequency-multiplexed quantum-information (QI) signal. This QI signal is applied by OM 116 to transmission link 120 and is received at receiver 130 as QI signal 128.
  • Receiver 130 has an OFCS 132 and an OM 136 that are generally analogous to OFCS 112 and OM 116, respectively, of transmitter 110.
  • OFCS 132 generates an optical signal 134 having a plurality of uniformly spaced frequency components, and OM 136 independently modulates each component of signal 134 to produce a multiplexed local-oscillator (LO) signal 138.
  • LO local-oscillator
  • Each of optical-frequency comb sources 112 and 132 is independently referenced to a frequency standard (e.g., an atomic clock) such that signals 114 and 134 have substantially the same (common) set of frequencies.
  • each of optical-frequency comb sources 112 and 132 provides a frequency comb, in which each frequency mode has (i) a spectral width of about 10 kHz or better and (ii) a center frequency located within about 100 Hz or less from a designated frequency defined with respect to the frequency standard.
  • Such sources have been developed in recent years and can be implemented, e.g., using carrier-envelope-offset (CEO) locked lasers.
  • CEO carrier-envelope-offset
  • QI signal 128 and LO signal 138 have frequency components belonging to substantially the same set of frequencies.
  • the former has relatively low intensity suitable for QKD, while the latter has relatively high intensity.
  • QI signal 128 and LO signal 138 have intensities of about 1 and 10 6 photons per pulse per component, respectively.
  • each of photo-detectors 150a-b comprises a de-multiplexer (DMUX) coupled to an array of photodiodes, with each photodiode in the array optically coupled to a separate output port of the DMUX.
  • DMUX de-multiplexer
  • each amplifier in array 160 is a differential amplifier configured to receive two electrical signals corresponding to the same frequency (channel) from photo-detectors 150a-b. As such, each amplifier in array 160 takes a difference between the received signals, amplifies it, and applies the amplified difference signal to a signal processor 170 for further processing.
  • optical coupler 140, photo-detectors 150a-b, and amplifier array 160 implement at receiver 130 a multi-channel homodyne detection scheme. For each frequency component of QI signal 128, this homodyne detection scheme provides quadrature measurements, from which quantum-bit values carried by the QI signal can be ascertained.
  • Fig. 2 graphically shows a phase-modulation format that can be used in system 100 according to one embodiment of the invention. More specifically, transmitter 110 (Alice) encodes quantum-bit values onto the QI signal applied to transmission link 120 by randomly applying in OM 116 a phase shift of 0, 90, 180, or 270 degrees to each frequency component of signal 114, with the phase shifts of 0 and 90 degrees associated with the binary "1" and the phase shifts of 180 and 270 degrees associated with the binary "0". For each quantum bit, in addition to encoding the bit value, the phase shift also determines Alice's basis set selection for that bit. For example, the modulation format of Fig.
  • the quantum-bit values carried by QI signal 128 are ascertained by randomly applying in OM 136 a phase shift of 0 or 90 degrees to each frequency component of signal 134 and then using the resulting LO oscillator signal 138 to implement the above-described homodyne detection scheme. For each quantum bit, the phase shift applied in OM 136 similarly determines Bob's basis set selection for that bit.
  • the phase vector corresponding to that bit is most likely to fall into circle 302, when the quantum bit is "1,” or into circle 306, when the quantum bit is "0.”
  • the phase vector corresponding to the bit is most likely to fall into circle 304, when the quantum bit is "I,” or into circle 308, when the quantum bit is "0.”
  • Bob's homodyne detection scheme implemented in receiver 130 is substantially equivalent to measuring a projection of the received phase vector onto Bob's selected basis set (Re or Im). If averaged over a sufficiently large number of quantum bits, the normalized output of each amplifier in array 160 is described by the probability distribution functions, e.g., similar to those shown in Figs. 3B-C .
  • Curve 348 shown in Fig. 3C represents the probability distribution functions that describe the normalized amplifier output when Alice and Bob select different basis sets. Note that, in contrast to Fig. 3B , now a single curve (curve 348 ) represents both probability distribution functions, i.e., the probability distribution function corresponding to "1" bits and the probability distribution function corresponding to "0" bits overlap, with the curve being Gaussian-like and centered at 0. Due to this probability-distribution-function degeneracy, Bob cannot differentiate between binary "ones" and "zeros," and the situation of Fig. 3C is often referred to as an "incorrect basis set selection" by Bob.
  • the resulting probability distribution function measured by Bob is a triple-humped curve similar to the curve representing a sum of curves 320, 348, and 360 ( Figs. 3B and 3C ).
  • the individual probability distribution functions represented by each of curves 320, 348, and 360 can be obtained in a training mode, as described in more details below.
  • receiver 130 interprets the measurement results as follows.
  • Bob tells Alice, via an authenticated public channel established, e.g., over a conventional telephone or computer network, his basis set choices, and Alice tells Bob which basis set choices were correct.
  • Bob retains the judgments corresponding to the correct basis set choices, while discarding the judgments corresponding to the incorrect basis set choices, to compile a sifted quantum key (also referred to as a raw key).
  • Alice and Bob carry out error correction and privacy amplification procedures with the sifted quantum key to distill a secure quantum key. Additional information on representative error correction and privacy amplification procedures can be found, e.g., in (1) F. Grosshans and P. Grangier, Phys. Rev.
  • Fig. 5 shows a method 500 of generating control signal 180 at receiver 130 of system 100 according to one embodiment of the invention.
  • transmitter 110 and receiver 130 of system 100 are configured to transmit and receive, respectively, a training signal having a training sequence of bits.
  • a training sequence can include any predetermined combination of bits known to both transmitter 110 and receiver 130 and transmitted using a known basis set selection.
  • the training sequence comprises a string of binary "ones" encoded in the modulation format of Fig. 2 with a 0-degree phase shift.
  • the training sequence is sufficiently long (e.g., 1000 bits) for processor 170 to have enough data to generate a probability distribution function, e.g., similar to one of those shown in Figs.
  • the training sequence may be transmitted on each frequency (channel) of system 100 or on selected few pilot frequencies (channels).
  • QKD frequencies When only pilot frequencies are used for the training sequence transmission, other frequencies (referred hereafter as QKD frequencies) may continue to be utilized for regular quantum-key data transmission in parallel with the training sequence transmission.
  • system 100 has one pilot frequency for every nine QKD frequencies.
  • processor 170 processes quadrature measurement results for each of the frequencies utilized in the training sequence transmission to generate, for each of those frequencies, a corresponding probability distribution function.
  • processor 170 may employ sliding-window processing to track the probability distribution function for each frequency over time. For example, suppose that the string of bits in the training sequence is 1000 bits long.
  • processor 170 can be configured to generate (i) a first probability distribution function based on the quadrature measurement results corresponding to 1-st to 100-th bits, (ii) a second probability distribution function based on the quadrature measurement results corresponding to 11-th to 110-th bits, (iii) a third probability distribution function based on the quadrature measurement results corresponding to 21-st to 120-th bits, etc.
  • processor 170 generates 91 probability distribution functions which, when taken together, reflect time evolution of the link and channel conditions and/or any phase-shift adjustments made in OM 136.
  • processor 170 evaluates, for each frequency, the probability distribution function(s) generated at step 504. Such evaluation may include determining a distribution average, median, full width at the half-maximum (FWHM), etc. Based on this evaluation, processor 170 generates control signal 180, which instructs OM 136 to set or adjust a reference phase shift value for each frequency to properly phase-lock the corresponding components of LO signal 138 and QI signal 128. In one configuration, processor 170 uses the above-described sliding-window processing to track the phase-lock between LO signal 138 and QI signal 128 in (quasi-)real time.
  • system 100 In a system configuration that utilizes all frequencies for the training sequence transmission, system 100 periodically switches between the training and QKD modes of operation.
  • system 100 establishes a phase lock for each frequency, e.g., as described above.
  • system 100 uses the phase lock established during the training mode to transmit quantum-key data on all frequencies.
  • the periodicity of mode switching in system 100 is typically governed by the condition of transmission link 120. For example, when ambient temperature along transmission link 120 is relatively stable, mode switching in system 100 can occur relatively infrequently. In contrast, when ambient temperature along transmission link 120 is subject to relatively strong fluctuations, mode switching in system 100 can occur more often.
  • a QKD protocol might include error-rate monitoring as a part of its error-correction and privacy-amplification routine, which enables dynamic adjustment of the periodicity of mode switching when the quality of the transmission link varies over time.
  • processor 170 In a system configuration that utilizes pilot frequencies for the training sequence transmission, processor 170 preferably tracks the phase lock between the LO signal 138 and QI signal 128 for each of the pilot frequencies in real time. For all other signal frequencies, processor 170 determines the reference phase shifts (preferably also in real time) by approximation (e.g., interpolation and/or extrapolation) from the current reference phase-shift values for the pilot frequencies. For example, in one configuration, processor 170 treats the reference phase shift values determined for the pilot frequencies as a set of discrete samples of a continuous function that describes frequency dependence of reference phase shifts for all signal frequencies. Processor 170 then computes that continuous function using a selected fitting technique (e.g., spline fitting) and samples the computed function at appropriate frequencies to determine reference phase shifts for the signal frequencies other than the pilot frequencies.
  • a selected fitting technique e.g., spline fitting
  • Figs. 6A-C and 7A-C graphically illustrate representative implementations of method 500. More specifically, Figs. 6A-C graphically illustrate representative homodyne-detection statistics at receiver 130 for a channel of system 100 configured to transmit a training sequence, when LO signal 138 is appropriately phase-locked to QI signal 128. Similarly, Figs. 7A-C graphically illustrate representative homodyne-detection statistics for that channel, when there is a phase-lock error between LO signal 138 and QI signal 128. Figs. 6A-C and 7A-C are generally analogous to Figs. 3A-C and 4A-C , respectively, with analogous figure elements designated by the labels having the same last two digits.
  • the training sequence corresponding to Figs. 6A-C and 7A-C comprises a string of binary "ones" encoded in the modulation format of Fig. 2 with a 0-degree phase shift (Re basis).
  • a phase-lock error of ⁇ degrees causes a phase-diagram rotation similar to that shown in Fig. 4A .
  • curve 720 Fig. 7B
  • curve 740 Fig. 7C
  • Bob is able to detect a phase-lock error by measuring a deviation of the distribution average from (or equivalently displacement of the corresponding probability distribution function with respect to) 1 and 0, respectively.
  • it is more advantageous for Bob to generate control signal 180 based on the value of ⁇ than that of ⁇ because (1) the displacement of curve 740 is measured with respect to zero and, therefore, the effect of possible normalization errors on the value of ⁇ is relatively small, (2) the sign of ⁇ can distinguish negative and positive values of ⁇ , while ⁇ cannot, and (3) for small values of ⁇ , ⁇ is significantly larger than ⁇ .
  • receiver 130 (Bob) is likely to achieve a better phase lock (i.e., a smaller phase-lock error) when processor 170 generates control signal 180 based on ⁇ , rather than ⁇ .
  • system 100 might implement method 500 as follows.
  • receiver 130 Bob
  • processor 170 is configured to generate probability distribution functions, e.g., using the above-described "sliding-window" processing.
  • processor 170 is configured to generate control signal 180 such that the distribution average for each frequency utilized for the training sequence transmission is nulled.
  • the phase shift in OM 136 corresponding to a null of the distribution average for a particular frequency is then designated as a reference phase shift for that frequency.
  • Processor 170 is configured to appropriately adjust, in real time, control signal 180 based on the "sliding-window" processing of step 504 to continuously track the nulls of the distribution averages, thereby appropriately adjusting the reference phase shifts.
  • method 500 results in reference phase shifts that produce a 90-degree phase shift for each frequency component of LO signal 138 with respect to a corresponding frequency component of QI signal 128. Consequently, the random phase shifts applied by OM 136 to each frequency component during regular QKD transmission are selected from -90 and 0 degrees with respect to the reference phase shift to obtain the phase shifts of 0 and 90 degrees, respectively, with respect to the 0-degree phase shift of the modulation format shown in Fig. 2 .
  • receiver 130 When transmission of QI signal 128 ( Fig. 1 ) is first initiated, receiver 130 (Bob) has no initial knowledge of the phases of the incoming signal. To acquire this initial knowledge, receiver 130 is configured to calibrate OM 136, i.e., to determine a correspondence between a phase shift introduced in the OM and the phase of the incoming QI signal. In one configuration, receiver 130 performs a calibration procedure, which involves, for each frequency component, performing a scan of phase shift values introduced by OM 136 into LO signal 138 over a phase shift interval of, e.g., 2 ⁇ , using sufficiently small increments of the relative phase shift, while receiving a training signal and tracking the value of the corresponding distribution average.
  • a calibration procedure which involves, for each frequency component, performing a scan of phase shift values introduced by OM 136 into LO signal 138 over a phase shift interval of, e.g., 2 ⁇ , using sufficiently small increments of the relative phase shift, while receiving a training signal and tracking the value of the corresponding distribution
  • system 100 can reduce the amount of time spent on training sequence measurements as follows.
  • System 100 can temporarily increase the number of photons in the training signal(s), under the limitation that such an increase does not substantially increase linear and/or nonlinear cross-talk among different frequency channels. Such an increase helps receiver 130 to measure the probability distribution function(s) in fewer time slots, thereby reducing the overall training time.
  • system 100 can be configured to operate using various QKD protocols, e.g., without limitation, a BB84 protocol, a B92 protocol, or a continuous-variable protocol.
  • QKD protocols e.g., without limitation, a BB84 protocol, a B92 protocol, or a continuous-variable protocol.
  • embodiments of the invention have been described in reference to phase modulation, one skilled in the art will appreciate that the invention can also be adapted for use with polarization modulation or modulation of any other suitable parameter of an optical signal.
  • Location of the light source used for the production of a LO signal is not necessarily limited to the receiver (Bob) and, in one embodiment, said light source can be located at the transmitter (Alice) or at other suitable location.

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Claims (10)

  1. Verfahren für den Empfang von Quanteninformationen an einem Empfänger (130) eines Kommunikationssystems mit einem Sender (110), der über eine Übertragungsstrecke (120) an den Empfänger gekoppelt ist, wobei das Verfahren umfasst:
    (A) Empfangen, über die Übertragungsstrecke eines von dem Sender unter Verwendung einer ersten optischen Quelle (112) erzeugten Quanteninformations- bzw. QI-Signals (128); und
    (B) Phasenregeln auf das QI-Signal eines an dem Empfänger unter Verwendung einer zweiten optischen Quelle (132) erzeugten Lokaloszillator- bzw. LO-Signals (138).
  2. ErFndung nach Anspruch 1, weiterhin umfassend:
    Kombinieren des LO-Signals und des QI-Signals, um ein erstes und ein zweites Interferenzsignal zu erzeugen;
    Messen einer Intensitätsdifferenz zwischen dem ersten und dem zweiten Interferenzsignal; und
    Phasenverschieban des LO-Signals auf der Basis des Messergebnisses, um die Phasenregelung auszuführen.
  3. Erfindung nach Anspruch 1, wobei:
    das QI-Signal für Schritt (A) ein Übungssignal umfasst; und
    Schritt (B) umfasst:
    Erzeugen einer dem Übungssignal entsprechenden Wahrscheinlichkeitsverteilungsfunktion;
    Bestimmen einer Referenzphasenverschiebung für das LO-Signal auf der Basis der Wahrscheinlichkedsverteilungsfunktion; und
    Phasenverschieben des LO-Signals unter Verwendung der Referenzphasenverschiebung, um die Phasenregelung auszuführen.
  4. Ertndung nach Anspruch 3, wobei Schritt (B) umfasst:
    Bestimmen eines Verteilungsdurchschnitts für die Wahrscheinlichkeitsverteilungsfunktion;
    Bestimmen der Referenzphasenverschiebung auf der Basis des Verteilungsdurchschnitts; und
    adaptives Nachführen einer Null des Verteilungsdurchschnitts.
  5. Erfindung nach Anspruch 1, wobei sowohl das QI-Signal als auch das LO-Signal eine Mehrzahl von Frequenzkomponenten aufweist, wobei:
    mindestens eine Frequenzkomponente des LO-Signals auf eine entsprechende Frequenzkomponente des QI-Signals phasengeregelt ist; und
    jede Frequenzkomponente des QI-Signals zwischen dem Transport eines Übungssignals und eines Signals mit Quantenschlüsseldaten wechselt.
  6. Erfindung nach Anspruch 1, wobei:
    Für Schritt (A), das QI-Signal eine oder mehrere Pilotfrequenzkomponenten aufweist, welche jeweils durch eine entsprechende optische Frequenz gekennzeichnet sind, wobei jedes Pilotfrequenzteil ein Übungssignal transportiert;
    für Schritt (B), das LO-Signal eine oder mehrere Pilotfrequenzkomponenten mit der einen oder den mehreren optischen Frequenzen aufweist;
    Schritt (B) für jede Pilotfrequenzkomponente des LO-Signals umfasst:
    Bestimmen einer Referenzphasenverschiebung auf der Basis des Übungssignals; und
    Phasenverschieben der Pilotfrequenzkomponente des LO-Signals unter Verwendung der Referenzphasenverschiebung.
  7. ErFndung nach Anspruch 6, wobei, für mindestens eine Frequenzkomponente des LO-Signals mit einer anderen Signalfrequenz als eine der optischen Frequenzen der einen oder mehreren Pilotfrequenzkomponenten, Schritt (B) das Bestimmen einer Referenzphasenverschiebung auf der Basis der einen oder mehreren für die eine oder mehreren Pilotfrequenzkomponenten des LO-Signals bestimmten Referenzphasenverschiebungen umfasst.
  8. Erfindung nach Anspruch 6, wobei, zusätzlich zu der einen oder den mehreren Pilotfrequenzkomponenten, sowohl das QI-Signal als auch das LO-Signal eine oder mehrere Quantenschlüsselverteilungs- bzw. QKD-Frequenzkomponenten aufweist, wobei das Verfahren das Empfang von Quantenschlüsseldaten, parallel zu dem einen oder mehreren Übungssignalen, unter Verwendung der besagten QKD-Frequenzkomponenten umfasst.
  9. Kommunikationssystem zur Übertragung von Quanteninformationen, umfassend einen über eine Übertragungsstrecke an einen Empfänger gekoppelten Sender, wobei der Empfänger für das Durchführen der folgenden Schritte ausgelegt ist:
    Empfangen, über die Übertragungsstrecke, eines von dem Sender unter Verwendung einer ersten optischen Quelle erzeugten Quanteninformations- bzw. QI-Signals: und
    Phasenverschieben eines unter Verwendung einer zweiten optischen Quelle am Empfänger erzeugten Lokaloszillator- bzw. LO-Signals auf das QI-Signal.
  10. Empfänger für ein Kommunikationssystem, welches für die Übertragung von Quanteninformationen ausgelegt ist und einen über eine Übertragungsstrecke an den Empfänger gekoppelten Sender aufweist, wobei der Empfänger für das Durchführen der folgenden Schritte ausgelegt ist:
    Empfangen, über die Übertragungsstrecke, eines von dem Sender unter Verwendung einer ersten optischen Quelle erzeugten Quanteninformations- bzw. QI-Signals; und
    Phasenverschieben eines unter Verwendung einer zweiten optischen Quelle am Empfänger erzeugten Lokaloszillator- bzw. LO-Signals auf das QI-Signal,
EP06769881A 2005-05-17 2006-04-25 Phasenregelung in einem mehrkanal-quantenkommunikationssystem Not-in-force EP1882332B1 (de)

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US68172605P 2005-05-17 2005-05-17
US11/210,941 US7706536B2 (en) 2005-05-17 2005-08-24 Phase locking in a multi-channel quantum communication system
PCT/US2006/015588 WO2006124209A1 (en) 2005-05-17 2006-04-25 Phase locking in a multi-channel quantum communication system

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EP1882332B1 true EP1882332B1 (de) 2012-08-08

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JP2014103514A (ja) * 2012-11-19 2014-06-05 Toshiba Corp 通信装置、通信システムおよびプログラム
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US20060262930A1 (en) 2006-11-23
JP5036707B2 (ja) 2012-09-26
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US7706536B2 (en) 2010-04-27
EP1882332A1 (de) 2008-01-30
CA2607318A1 (en) 2006-11-23

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